As next generation candidates for a lithography technique used during a manufacturing process of a semiconductor element, there have been known a double patterning technique using ArF immersion exposure, EUV lithography, nanoimprinting, and so on. These lithography techniques include various problems such as increase in cost and reduction in throughput caused by miniaturization of a pattern.
Under such a situation, application of self-assembly (DSA: Directed Self-assembly) process to the lithography technique has been expected. The self-assembly is induced by such an autonomous behavior as energy stabilization, so that a pattern with high dimensional accuracy can be formed. Particularly, in the techniques using microphase separation of a polymeric block copolymer, periodical structures having various shapes with a size of several to several hundred nm (nanometer) can be formed by simple coating and an annealing process. The form of the polymeric block copolymer is changed into a spherical shape, a cylindrical shape, a lamellar shape, or the like based on a composition ratio of a block of the polymeric block copolymer, and the size of the polymeric block copolymer is changed based on a molecular weight, whereby a dot pattern, a hole or pillar pattern, a line pattern, and so on having various sizes can be formed.
In order to form a desired pattern over a wide range with the use of DSA, a guide for controlling an occurrence position of a polymer phase formed by self-assembly is required to be provided. As the guide, there have been known a physical guide (graphoepitaxy) having a concavoconvex structure with respect to a substrate surface and forming a microphase separation pattern in a space pattern and a chemical guide (chemo epitaxy) formed in a lower layer of a DSA material and controlling a microphase separation pattern formation position based on a difference in the interfacial surface energy.
The microphase separation pattern is formed with respect to a previously formed guide pattern. Thus, in order to form an extremely fine microphase separation pattern, formation of a guide pattern including a fine pattern is required. However, it has been difficult to form the guide pattern including the fine pattern.
The chemical guide has a first pattern member (hereinafter referred to as a neutralization layer) whose interfacial surface energy against a first segment of a self-assembly (DSA) polymer is the same as the interfacial surface energy against a second segment of the DSA polymer and a second pattern member (hereinafter referred to as a pinning layer) whose interfacial surface energy against the first segment is different from the interfacial surface energy against the second segment, and the first and second pattern members are formed into a predetermined pattern.
Since the pinning layer has a high affinity for one of the segments of the self-assembly polymer, only the segment is drawn to the pinning layer. The use of this phenomenon can realize the disposition of a polymer phase at a desired position. This is the principle of a position control using the chemical guide.
Since the position control of the DSA pattern significantly depends on the pattern of the pinning layer, the pinning layer is required to have high pattern accuracy.
For example, it is desirable that the width of the pattern of the pinning layer is comparable to the width of the DSA pattern. However, it is extremely difficult to form a pattern, which is comparable to a resolution desired to be achieved in DSA, with the use of optical lithography. Thus, there has been known a method of applying slimming treatment to a pattern previously formed by the optical lithography and thereby obtaining a pinning layer pattern having a desired pattern width. However, in this method, LER (Line Edge Roughness) and LWR (Line Width Roughness) become problems.
When the pinning layer pattern is formed by the optical lithography, the pitch of the pinning layer pattern cannot exceed the resolution limit of the optical lithography, and therefore, the pitch of the pinning layer pattern is significantly increased relative to the pitch of the polymer phase of the DSA pattern, so that the position control accuracy as the chemical guide is reduced.
It is preferable that the pitch of the pinning layer pattern is n times (n is natural number) the pitch of the DSA pattern. Presently, a chemical guide in which n=4 has been proposed. However, the smaller n (the smaller the pitch of the chemical guide), the higher the position control accuracy as the chemical guide; therefore, the formation of a chemical guide having a small pitch and a fine pattern is required.
The miniaturization of the width and pitch of the pinning layer pattern are required in a physical guide as well as the chemical guide. In the method of pattern formation using the physical guide, when the DSA pattern is formed using a block copolymer, there is a problem that a line-and-space pattern in which the line width:the space width is 1:1 cannot be formed.